1. Single-Stranded siRNAs Activate RNAi in Animals
Walt F. Lima, Thazha P. Prakash, Heather M. Murray, Garth A. Kinberger, Wenyu Li, Alfred E. Chappell, Cheryl S. Li, Susan F. Murray, Hans Gaus, Punit P. Seth, Eric E. Swayze, Stanley T. Crooke 
Cell 
Volume 150, Issue 5, Pages (August 2012)
DOI: /j.cell
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2. Cell  , DOI: ( /j.cell )
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3. Figure 1
Modified Nucleic Acid Composition, In Vitro Potencies, and Half-Lives of Potent ss-siRNAs
(A) Configuration of the optimized chemically modified ss-siRNA includes: metabolically stable 5′ phosphonate analog (I); 2′-MOE-modified 5′-terminal nucleotide for protection from 5′ exonuclease activity (II); alternating 2′-F and 2′-OMe motifs with contiguous PS modifications at the 3′ pole and alternating PS and PO motifs at the 5′ pole of the ss-siRNA for protection from endonuclease activity (III); 2′-MOE-modified adenosine dinucleotide at the 3′ terminus for protection from 3′ exonuclease activity and enhanced potency (IV); and C16 modification for enhanced tissue distribution (V). The color coding of the modified nucleotides is as described in (B). Following either subcutaneous or intravenous administration, the ss-siRNA distributed to peripheral tissues and engaged the RNAi mechanism to degrade the target mRNA.
(B) Nucleotide modifications include: phosphorothioate (PS), 2′-fluororibose (green, 2′-F), 2′-methoxyribose (blue, 2′-OMe), 2′-methoxyethylribose (orange, 2′-MOE), 5′-methylenephosphonate (red, 5′-MP), 5′-(E)-vinyl-phosphonate (red, 5′-VP), C10 (TC10), and C16 (TC16).
(C) Nucleotide modifications are described in (B). The siRNAs were prepared using a complementary RNA sense strand (5′-AAGUAAGGACCAGAGACAA-3′). The in vitro potencies (IC50) correspond to the ss-siRNA or siRNA concentration, resulting in 50%reduction of the PTEN mRNA level compared to lipid-only treated cells. Data are represented as mean ± SD. The metabolic half-lives (t1/2) of the ss-siRNAs are defined as the incubation time in primary hepatocyte homogenates, resulting in 50% loss of the full-length ss-siRNA. ND, not determined.
See also Table S1 and Figures 1 and 5.
Cell  , DOI: ( /j.cell )
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4. Figure 2 Ago2 Cleavage Activities of Chemically Modified ss-siRNAs
(A) Scheme for cleavage of ss-siRNA by Ago2. The ss-siRNA was bound to the enzyme prior to adding the target RNA. Ago2 containing the ss-siRNA was incubated with the 32P-labeled target RNA. Double-stranded siRNAs were not tested, as they do not bind recombinant human Ago2.
(B) Relative recombinant human Ago2 cleavage activity for various ss-siRNAs. Cleavage activities of the ss-siRNAs are reported as a ratio of the cleavage activity observed for the unmodified ss-siRNA1. Data are represented as mean ± SD.
(C) PAGE analysis of 32P-labeled 40 nucleotide target RNA and human Ago2 cleavage products (red arrow). The position of the Ago2 cleavage site (red arrow) in the target RNA (black sequence) is shown relative to the ss-siRNA (gray sequence).
Cell  , DOI: ( /j.cell )
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5. Figure 3
Identification of ss-siRNA Metabolites Extracted from Hepatocyte Homogenates or Mouse Liver
(A) Liquid chromatography-tandem mass spectrometry (LC-MS) analysis of the ss-siRNA 5 extracted from hepatocyte homogenates 1 hr posttreatment.
(B–E) LC-MS of ss-siRNAs 7 (B), 8 (C), 26 (D), and 27 (E) extracted from mouse liver 48 hr posttreatment. The liquid chromatography profiles show the relative abundance of the metabolites identified by mass spectrometry compared to the internal standard (Int. Std.). Numbered arrows indicate the position of degradation sites in the ss-siRNA in relationship to the corresponding peaks from the liquid chromatography profile.
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6. Figure 4
ss-siRNA Activity Is Ago2 Dependent and Requires a 5′ Phosphate
(A) The position of the cleavage site within the PTEN mRNA from cells treated with ss-siRNA 8 was determined using 5′-RACE. Sequencing results are shown in the top panel. The red sequence corresponds to the 5′-RACE adaptor and the black sequence to the downstream cleavage product of the PTEN mRNA. The position of cleavage is identified as the junction between the 5′-RACE adaptor and the PTEN mRNA (red line). The sequence below shows the position of cleavage site (arrow) on the PTEN mRNA (black sequence) in relation to the hybridization site for the ss-siRNA (gray sequence).
(B) 5′-terminal modifications include: 5′ phosphate (5′-P), 5′ hydroxyl (5′-OH), 5′ methoxy (5′-OMe), 5′ deoxy (5′-H), and 5′ fluoro (5′-F). The siRNAs were prepared and the in vitro potencies in HeLa cells reported as in Figure 1. ND, not determined.
(C) Dose-dependent reduction of PTEN mRNA from wild-type (gold) and Ago2 knockout (blue) mouse embryonic fibroblast cells (MEF) transfected with the ss-siRNA 8 (solid circle) or corresponding siRNA (solid square). PTEN mRNA levels are reported as a percentage of the PTEN mRNA levels for the lipid-only-treated cells.
(D) Human Ago2 cleavage activities of ss-siRNA are reported as described in Figure 2.
See also Table S1 and Figures S2, S3, and S4. Data are represented as mean ± SD.
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7. Figure 5 Potency of ss-siRNA in Hepatocytes and Efficacy in Mice
(A) The in vitro potencies (IC50) of the ss-siRNAs targeting PTEN (I), Factor VII (II), or ApoCIII (III) mRNAs were determined using primary hepatocytes.
(B) The PTEN mRNA levels from the livers of mice treated with either 300 mg/kg (back bars) or 100 mg/kg (red bars) of the ss-siRNAs are reported as a percentage of the PTEN mRNA from the saline-treated group. The Factor VII (blue bar) or ApoCIII (green bar) mRNA levels from the livers of mice treated with 300 mg/kg of the Factor VII or ApoCIII ss-siRNAs, respectively.
(C) Liver concentrations of the PTEN ss-siRNAs were measured from mice treated with either 300 mg/kg (black bars) or 100 mg/kg (red bars). Liver concentrations of the Factor VII (blue bar) or ApoCIII (green bar) ss-siRNAs were measured from mice treated with 300 mg/kg.
ND and I indicate not determined and inactive, respectively. Data are represented as mean ± SD.
See also Tables S1 and S2.
Cell  , DOI: ( /j.cell )
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8. Figure 6
In Vivo Activities of Modified ss-siRNAs following Single-Dose Administration
(A) The position of the cleavage site within the PTEN mRNA from mice treated with the ss-siRNA 27 was determined using 5′-RACE. The procedure and interpretation of the results are as described in Figure 4A.
(B) Dose-dependent reduction of PTEN mRNA from liver of mice (n = 4) treated with a single dose of either ss-siRNAs 27 (green bars) or 29 (purple bars) administered subcutaneously and sacrificed 48 hr posttreatment.
(C and D) Duration of action (C) and tissue half-life (D) of the ss-siRNA 27 in mouse liver. Mice (n = 4) were treated with 100 mg/kg ss-siRNA 27 by subcutaneous administration and sacrificed at 1, 2, 3, 10, and 30 days posttreatment. Liver PTEN mRNA levels (C) are reported as a percentage of the PTEN mRNA levels for the saline-treated control group and the ss-siRNA 27 concentrations in the liver (D) for each time point.
(E) On- and off-target activities from livers of the mice treated with 300 mg/kg of the ss-siRNAs targeting PTEN (27), Factor VII (31), or ApoCIII (32). The PTEN (gold bar), Factor VII (tan bar), and ApoCIII (peach bar) mRNA levels were determined for all ss-siRNA-treated mice and reported as a percentage of the respective mRNAs levels from the saline-treated group.
(F) Reduction of PTEN mRNA from the peripheral tissues of mice treated with 100 mg/kg of the ss-siRNAs 27 or 29. The PTEN mRNA levels from kidney (dark blue), quadriceps (medium blue), lung (light blue), and fat (light green).
Data are represented as mean ± SD.
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9. Figure 7
In Vivo Activities of Modified ss-siRNAs following Multiple-Dose Administration
(A) Dose-dependent reduction of PTEN mRNA from liver of mice (n = 4) treated with ss-siRNA 29 by either subcutaneous (red bars, SQ) or intravenous (blue bars, IV) administration. The ss-siRNA was dosed twice a week for 3 weeks, and the doses reported are per injection.
(B and C) Aminotransferase (B) and bilirubin (C) levels from the mice described in (A) treated with the ss-siRNA 29 by either subcutaneous (red bars) or intravenous (blue bars) administration.
Data are represented as mean ± SD.
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10. Figure S1
Structure of Modified Nucleoside Phosphoramidites Used in This Study, Related to Figure 1B
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11. Figure S2
Synthesis of 5′-O-Methyl-2′-O-(2-Methoxyethyl)-5-Methyluridine-3′-[(2-Cyanoethyl)-N,N-Diisopropyl] Phosphoramidite 4, Related to Figure 4B
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12. Figure S3
Synthesis of 5′-Deoxy-5′-Fluoro-2′-O-(2-Methoxy Ethyl)-5-Methyl Uridine-3′-[(2-Cyanoethyl)-N,N-Diisopropyl] Phosphoramidite 5, Related to Figure 4B
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13. Figure S4
Synthesis of 5′-Deoxy-2′-O-(2-Methoxyethyl)-5-Methyl Uridine-3′-[(2-Cyanoethyl)-N,N-Diisopropyl] Phosphoramidite 6, Related to Figure 4B
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14. Figure S5
Synthesis of 5′-O-(4,4'-Dimethoxytrityl)-2′-O-[6-(N-Decanoyl) Amino) Hexyl]-5-Methyluridine-3′-[(2-Cyanoethyl)-N,N-Diisopropyl] Phosphoramidite 9a, 5′-O-(4,4'-Dimethoxytrityl)-2′-O-[6-(N-Hexadecanoyl)Aminohexyl]-5-Methyluridine-3′-[(2-Cyanoethyl)-N,N-Diisopropyl] Phosphoramidite 9b, Related to Figure 1B
Cell  , DOI: ( /j.cell )
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